Conventional operating systems include shells that provide user interfaces. Unfortunately, such shells are often limited in their capabilities and in the flexibility of options that they provide to an applications developer. For example, such conventional operating systems often provide shells that define context menus for each file system object. The list of menu items and associated operations provided by the shells for the context menus are often limited. Moreover, the menu items cannot be changed by applications.
Conventional shells are often additionally limited in that they predefine property sheet pages for file system objects. The property sheet pages are user interface elements that display property values for the associated file system objects and typically allow a user to change some of the displayed property values. Each property sheet page is associated with a subset of related properties for the objects.
The shells of conventional operating systems are further limited in that they provide predefined icons only for file types or objects classes. These shells do not facilitate the use of per-instance icons that are associated with each instance of an object or file. The shells of the conventional operating systems are further limited in that they only provide access to objects in the file system name spaces and provide no easy mechanism for integrating additional name spaces into the system.
Conventional operating systems are also limited as to drag-and-drop operations. In particular, applications have no ability to customize the functionality of a drop based upon a file object type in conventional systems. Further, these conventional operating systems provide no ability to customize source objects in drag-and-drop operations.